The present invention relates to a steer-by-wire system and method for actuating road wheels of a vehicle.
Vehicle steer-by-wire systems are widely known. A typical steer-by-wire system may include a driver interface, e.g., a steering wheel or a steering joy stick, which is electrically linked to the road wheels of the vehicle. In some steer-by-wire systems, steering inputs at the driver interface are electronically transmitted to an actuating device connected to steering linkages to rotate the road wheels. For example, a steering input from the driver interface may be transmitted by wire to an electronic control unit or a microcontroller which then sends by wire a positioning command to a motor producing steering movement to a steering linkage of the vehicle, e.g., a front axle steering linkage to rotate the road wheels.
Although many current steer-by-wire systems are adequate, improvements may be made on such systems. Failure of steer-by-wire actuators or motors is one concern. Manufacturers have responded to such concern by providing steer-by-wire systems with strategies and control systems in an event of a device failure or system failure. Manufacturers have configured steer-by-wire systems with backup systems, redundancies, hydraulic systems, and/or backup power supplies. However, such added devices and systems require relatively large volume density and relatively high costs.
It has been determined that an increase in electric power capacity of a motor, requires an exponential increase in volume density of the motor. Thus, manufacturers have been challenged in providing a steer-by-wire system having an improved fail-safe system which reduces typical volume density requirements and maintains low costs.
Thus, it is an aspect of the present invention to provide a steer-by-wire system and method for actuating a steering linkage assembly connected to road wheels of a vehicle. The system has fail-safe capabilities for device and system failures.
It is another aspect of the present invention to provide a steer-by-wire system and method for actuating a steering linkage assembly connected to road wheels of a vehicle. The system has units of operation requiring relatively reduced volume density.
In one embodiment, the present invention is a steer-by-wire system for actuating a steering linkage assembly connected to road wheels of a vehicle. The system comprises the steering linkage assembly which includes an input shaft electrically connected to a driver interface, an output shaft connected to road wheels of the vehicle, and a gear unit linking the input and output shafts to rotate the road wheels.
The system further comprises a microcontroller for controlling an actuation strategy including normal and fault detection modes. The microcontroller is in electrical communication with a driver interface, e.g., a steering wheel. The microcontroller is configured to receive a steering signal indicative of steering input at the driver interface. The system further includes first and second power electronic drivers in electrical communication with the microcontroller for electrical power supply. The system further includes a first motor and a second motor for simultaneous operation with the steer-by-wire steering device. The first motor is in electrical communication with the first power electronic driver to receive electric power therefrom and the second motor is in electrical communication with the second power electronic driver to receive electric power therefrom. The first and second motors are connected to the input shaft to move the input shaft for linear movement of the output shaft to rotate the road wheels based on the steering signal. The first and second motors are configured to cooperate simultaneously to rotate the road wheels during the normal mode.
Further aspects, features and advantages of the invention will become apparent from consideration of the following description and the appended claims when taken in connection with the accompanying drawings.